Phosphate-containing ceramic structures for catalyst support and fluid filtering

ABSTRACT

A monolithic ceramic structure, useful as a support for catalytic material or as a fluid filter, has a high surface area phase which consists essentially of a porous metal oxide material, at least 50% by weight of which is alumina, titania, and/or zirconia, and phosphate dispersed substantially througout the porous metal oxide material. The presence of the phosphate stabilizes the porous metal oxide material against thermal degradation during sintering or exposure to elevated temperatures encountered in catalytic service and thereby aids in the retention of higher overall surface area in the monolithic structure.

BACKGROUND OF THE INVENTION

This invention is directed to high surface area monolithic structurescomposed of sintered ceramic oxide materials which have high porosity.The structures are useful as filters for fluids and as catalyticsubstrates in that they provide high surface area for particularfiltration or for deposition of catalytic material. The invention ismore particularly directed to structures in which the ceramic materialis primarily alumina, titania, or zirconia which has been modified,prior to firing or sintering, by admixture with a phosphate materialthat generates P₂ O₅ upon heating. The structures are particularlyuseful as catalyst supports in the conversion of automotive exhausts andin reduction of NOx emissions from industrial sources, and as fluidfilters, such as those used in diesel engines.

Conventional monolithic ceramic catalyst supports consist of anunderlying ceramic support material with a coating of high surface areamaterial upon which the catalyst itself is actually deposited. Inparticular, the ceramic support is prepared by sintering a mold of clayor other ceramic oxide (alumina, titania, cordierite, etc.) at atemperature sufficiently high to densify and strengthen the material.Temperatures high enough to result in effective sintering, however, alsocause pore shrinkage and other microstructural changes that result inthe sintered material's having a very low surface area. Consequently,the sintered ceramic must be coated with another material having ahigher surface area, often a ceramic material itself that has not beensintered or pre-reacted, on which to actually deposit the catalyst. Thisprocedure of applying a high surface area "wash-coat" on the low surfacearea ceramic wall is disclosed, for example, in U.S. Pat. Nos. 2,742,437and 3,824,196.

In addition to the exposure to high temperature during sintering,however, catalyst support structures can also be exposed to elevatedtemperatures in service. The surface area of a wash-coat can besubstantially degraded, and the surface area of the underlying ceramicmay also further be reduced in some instances, because of the highservice temperatures, such as those of automotive exhaust gases, towhich they are exposed. It is therefore desirable to use ceramicmaterials that are, or can be modified to be, resistant to loss ofsurface area when exposed to elevated temperatures either during firingor service. One such material is a mixture of 50-93% by weight aluminaand 7-50% by weight silica as disclosed in U.S. Pat. No. 4,631,269(Lachman et al, issued Dec. 23, 1986).

It is an object of the present invention to provide an improvedmonolithic structure that can be sintered to provide structural strengthand integrity without loss of appreciable surface area. It is a furtherobject of the invention to provide a structure that resists thermaldegradation of its porosity and available surface area despite exposureto elevated temperatures in catalytic conversion processes.

SUMMARY OF THE INVENTION

The present invention provides an improved monolithic structure, usefulas a filter or catalyst support, comprising (1) a sintered ceramic phaseof a porous metal oxide, at least 50% by weight of which is alumina,titania, and/or zirconia, and (2) about 0.5-35% by weight of P₂ O₅(based on the total weight of the P₂ O₅ and the alumina, titania, and/orzirconia) substantially dispersed throughout the porous metal oxidephase. In preferred embodiments directed to its use as a catalystsupport structure, the monolith further contains catalytic metals, suchas transition metals (including rare earth metals), or their oxides,distributed throughout the sintered ceramic phase of porous metal oxideor on the surfaces of the porous metal oxide.

The combination of P₂ O₅ with ceramic oxide material as described hereinprovides a supporting substrate for catalyst that retains high surfacearea and effective pore size distribution despite being subjected to theelevated temperatures of ceramic firing and catalytic service. Efficientcatalytic activity, which is dependent on surface area and porosity, cantherefore be maintained over longer service periods.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graph depicting the surface area retained, after firing, ofa P₂ O₅ -containing alumina material of the present invention.

FIG. 2 is a graph depicting the surface area retained, after firing, ofa P₂ O₅ -containing titania material of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

According to the present invention, a sintered monolithic structure isprovided which comprises a high surface area of porous ceramic metaloxide, at least 50% by weight of which is alumina, titania, and/orzirconia, and about 0.5-35% by weight of P₂ O₅ or equivalentphosphate-containing compound dispersed substantially throughout theporous metal oxide material. The structure is prepared by admixing theporous oxide material and a phosphate material capable of generating P₂O₅ at or below the firing temperature, forming the admixture into adesired shape, and firing the shape according to conventional techniquesof the ceramic arts to form a structure having substantial strength andhigh surface area. It has been found that the presence of the phosphatematerial, in intimate mixture with the ceramic porous oxide material,permits the oxide to be fired to an effective level of strength whileretaining an acceptable surface area and catalytically-effective poresize distribution.

The porous oxide materials suitable for use are those which, aftercalcining, have a surface area of at least 20 square meters per gram,preferably at least 100 square meters per gram, and most preferably atleast 200 square meters per gram. (As used herein, "calcining" meansheating a material to a temperature sufficiently high to substantiallyeliminate volatiles but below the temperature at which the materialbegins to densify.) At least 50% by weight of the porous oxide materialis alumina, titania, zirconia, or a mixture of these three. The balance,if any, of the porous oxide material can be any other ceramic materialthat has commonly been used as a catalyst support in the past and whichhas the above-described characteristics. Preferably, the porous oxidematerial is at least 75-80% by weight of alumina, titania, and/orzirconia (hereinafter, the "core metal oxides"). In particularlypreferred embodiments, substantially all the porous oxide material isone or more of these core metal oxides.

The aluminas useful as the porous metal oxide are those which, uponcalcining or firing, provide gamma-alumina or other transition aluminashaving the specified surface area. Colloidal gamma-alumina can be useddirectly or materials which generate a transition alumina uponcalcining, such as alpha-alumina monohydrate or alumina trihydrate, canalso be used. The colloidal gamma-alumina is generally in the form ofparticles of 1 micron size or less. When alpha-alumina monohydrate oralumina trihydrate is used, the particle size can be from less than 1micron up to 100 microns, but preferably less than about 75-80 microns.Suitable commercially available materials of this kind are Kaiser SAsubstrate alumina, CATAPAL alumina available from Vista ChemicalCompany, and DISPURAL alumina monohydrate from Remet ChemicalCorporation.

The alumina component can also be introduced in the form of a precursorsuch as a hydrated alumina, a hydrolyzed aluminum alkoxide, or aluminumchlorohydrate. The hydrated aluminas are preferably in the form of anaqueous suspension and are commercially available, for example, from theEthyl Corp. The most preferable aluminum alkoxide is hydrolyzed aluminumisopropoxide, which is commercially available as a dispersion inalcohol. For example, a dispersion of aluminum isopropoxide, 30-35% byweight in isobutanol, is available from the Alpha Products Division ofMorton Thiokol Inc. Aluminum chlorohydrate is available in the form ofan aqueous solution, for example, as CHLORHYDROL 50% or REHABOND CB-65Sfrom Reheis Chemical Co. Aluminum chlorohydrate is also available insolid particulate form, for example as CHLORHYDROL Powder from ReheisChemical Co.

High surface area titanias suitable for use as the ceramic porous metaloxide of this invention are commercially available, for example, fromthe Degussa Corporation as P25 TiO₂. The titania can also be introducedin the form of a precursor such as a suspension of an amorphous hydratedtitanium oxide, which can be in the form of a hydrolyzed titaniumalkoxide, such as titanium isopropoxide (tetraisopropyl titanate), or aslurry of titanium hydrate. Slurries of titanium hydrate arecommercially available, for example from SCM Corp. In all cases, thesolid titania or solid portion of the titania precursor is generally inparticulate form with a primary particle size less than about 100microns, preferably less than about 75-80 microns, and more preferablyless than 20 microns.

The zirconia material useful in the practice of the invention cangenerally be in any form heretofore used in the ceramic arts. Generally,a pre-reacted zirconia in particulate form with a primary particle sizein the same ranges as described immediately above is used. The zirconiacan also be added in the form of a precursor. The preferred precursor isa suspension of an amorphous hydrated zirconium oxide, which can be inthe form of a hydrolyzed zirconium alkoxide (such as zirconiumn-propoxide) or a slurry of zirconium hydrate.

Up to 50% by weight of the porous metal oxide material of the monolithcan be composed of one or more ceramic metal oxides other than theabove-described core metal oxides. This component of the monolith can beany of the well-known sinterable materials capable of providingmechanical strength and thermal properties in monolithic supports asheretofore prepared by those skilled in the art. Preferably thismaterial is selected from cordierite, mullite, clay (preferably kaolinclay), talc, spinels, silicates such as lithium alumino-silicates, alphaalumina, aluminates, aluminum titanate, aluminum titanate solidsolutions, stabilized zirconias, silica, glasses, and glass ceramics.Any mixture or combination of these materials can be used.

Spinels useful in the present invention are the magnesium aluminatespinels heretofore used as catalyst supports, including spinel solidsolutions in which magnesium is partially replaced by such other metalsas manganese, cobalt, zirconium, or zinc. Preferred spinels aremagnesium aluminate spinels having 1-7% by weight alumina in excess of1:1 MgO.Al₂ O₃ spinel; that is, those having about 72.0-73.5 weightpercent Al₂ O₃ (balance MgO). Spinels of this kind can be prepared bycoprecipitation or wet-mixing of precursors of alumina and magnesia,followed by drying and calcining. Such a procedure is described in U.S.Pat. No. 4,239,656, the disclosure of which is hereby incorporated byreference as filed. As a supplement to this disclosure, however, it hasbeen found that calcining of the spinels should normally not exceed1300° C. for 2-2.5 hours. Calcining temperatures below 1200° C. arepreferred. Suitable alumina precursors for preparation of the spinelsare hydrolyzed aluminum alkoxides or hydrated aluminas, both of whichare commercially available. Magnesium oxide component powders found tobe suitable are magnesium hydroxide slurry, about 40 weight percent MgO,available from Dow Chemical Company, or hydrated magnesium carbonate.

High surface area silicas that can be used in the practice of thepresent invention are the amorphous silicas of about 1-10 microns orsub-micron particle size such as Cabosil® EH-5 colloidal silica,available from Cabot Corporation. Colloidal silica derived from gels,such as Grade 952 from the Davison Chemical Division of W. R. Grace &Co. can also be used.

Cordierite, one of the preferred ceramic materials for use as theadditional substrate material herein, can be in the precursor or "raw"form which becomes true cordierite upon heating, or can be used inpre-reacted form. When raw cordierite is used, it is preferred that upto 10% by weight, based on cordierite weight, of B₂ O₃ be added to thebatch to initiate cordierite formation at lower than usual temperaturesand to impart additional strength.

Unless otherwise specified above, these additional ceramic materialsshould be in particulate form, preferably of a size finer than 200 mesh(U.S. Standard) and more preferably finer than 325 mesh (U.S. Standard).With such characteristics, the ceramic material can be more easilysintered, during the subsequent formation of the monolith, attemperatures below those at which surface area of these materials, aswell as the core metal oxides, might be adversely affected.

The phosphate component of the invention is incorporated into themonolith by admixing into the starting batch a compound capable ofgenerating P₂ O₅ at or below the firing or sintering temperature to beused. The source of the phosphate is not critical. Phosphoric anhydrideitself or phosphoric acid can be added, or a phosphate precursor,preferably one soluble in water, can be used. Preferred precursors ofthis kind are (NH₄)₂ HPO₄ (dibasic ammonium phosphate) and Al(H₂ PO₄)₃(aluminum dihydrogen phosphate).

Generally, the phosphate material is added to the batch in an amountthat will provide about 0.5-35% by weight of P₂ O₅, based on thecombined weights of P₂ O₅ and the core porous oxides. Preferably, thefinal weight of P₂ O₅ in the monolith will be about 1-25 weight percent.When substantially all of the core porous oxide is alumina, a morepreferred final weight percentage of P₂ O₅ is about 1-10%, and mostpreferably 3-7%. When the core porous oxide is substantially alltitania, a more preferred final weight percentage of P₂ O₅ is about1.5-15%, and most preferably about 3-10%. When substantially all of thecore porous oxide is zirconia, a more preferred final weight percentageof P₂ O₅ is about 1.5-15%.

The monolithic structures of this invention are prepared by admixinginto a substantially homogeneous batch (a) the porous metal oxidematerial, (b) the phosphate-generating material, and optionally (c) atemporary binder. Preferably, 1-30% by weight of temporary binder, basedon the total batch weight, is used. Any binder material conventionallyused in ceramic catalyst support manufacture is suitable. Preferred arebinders that are decomposed and burned-off at temperatures of about250°-600° C. Examples are disclosed in: "Ceramic Processing BeforeFiring," ed/by George Y. Onoda, Jr. & L. L. Hench, John Wiley & Sons,New York; "Study of Several Groups of Organic Binders Under Low-PressureExtrusion," C. C. Treischel & E. E. Emrich, Jour. Am. Cer. Soc. (29),pp. 129-132, 1946; "Organic (Temporary) Binders for Ceramic Systems," S.Levine, Ceramic Age, (75) No. 2, pp. 39+, January 1960; and "TemporaryOrganic Binders for Ceramic Systems" S. Levine, Ceramic Age, (75) No. 2,pp. 25+, February 1960. The most preferred binder is methyl cellulose,available as METHOCEL A4M from the Dow Chemical Co.

Mixing of the batch ingredients is preferably performed in a step-wiseprocedure in which any dry ingredients are first blended together. Thispreliminary dry-blending operation can be performed in any conventionalmixing equipment, but the use of a Littleford intensive mixer ispreferred. The dry mixture is then plasticized by being further mixed,preferably in a mix muller, with a liquid medium (preferably water)which acts as a plasticizer. During this stage, all remainingconstituents are added. Up to about 1% by weight, based upon totalmixture weight, of a surfactant such as sodium stearate can also beadded to facilitate mixing and flow for subsequent processing. Mixing ofall constituents should be continued until a homogeneous orsubstantially homogeneous plasticized mass is obtained.

To effect further mixing, the plasticized batch can be extruded througha "spaghetti" die one or more times. Ultimately, the batch is formedinto the desired "green" shape for the monolithic structure, preferablyby extrusion through a die or by injection molding. The materialprocessing method of this invention is particularly well suited to thepreparation of structures in the shape of thin-walled honeycombs andwagon-wheels. The preferred shape is that of a honeycomb having about25-2400, more preferably 200-400, through-and-through cells per squareinch of frontal surface area (equivalent to about 4-370, more preferablyabout 30-60, cells per square centimeter of surface area).

Finally, the "green" structures are fired in order to harden thematerial. The firing step generally takes place at 500°-1200° C.,although the use of temperatures below about 1100° C. are preferred. Formost ceramic materials, the temperature selected and the duration of thefiring period will result in actual sintering of the material. This ispreferred but not necessary. The strength requirements of the intendedend use of the structure will determine for the skilled artisan whetherthe additional densification and hardening provided by fully sinteringthe material will be necessary. The firing/sintering step can beconducted in an inert atmosphere or in one which promotes eitherreduction or oxidation, depending on the presence and identity ofcatalytically active metal compounds in the batch, as discussed morefully below. Optionally, the firing/sintering step can be preceded bydrying the shapes at about 100°-120° C., preferably by steam heat.

In the fired article, the P₂ O₅ is dispersed substantially throughoutthe porous metal oxide material. As those skilled in the art willrecognize, however, the P₂ O₅ may not necessarily exist as a free phasebut may combine with the porous metal oxide materials to form phosphatecompounds or complexes. For example, AlPO₄ and 5TiO₂.2P₂ O₅ are thecommon result of firing a phosphate-generating material with alumina andtitania, respectively. In one particularly preferred embodiment of thisinvention, the final monolith consists essentially of alumina and about4-23% by weight AlPO₄. In another particularly preferred embodiment, thefinal structure consists essentially of titania and about 5-12% byweight 5TiO₂.2P₂ O₅. The presence of P₂ O₅ dispersed substantiallythroughout the ceramic metal oxide material aids its retention of highsurface area despite elevated firing, sintering, or servicetemperatures. This benefit is illustrated in the Figures. Withparticular reference to FIG. 1, there is shown a graph of temperaturesversus surface area retained after a 6-hour heat soak for a batchmaterial consisting of 100% alumina and a batch material consisting of87% by weight alumina and 13% by weight AlPO₄. In FIG. 2 there is showna graph of temperature versus surface area retained after a 6-hour heatsoak for a batch material of 100% titania and a batch material of 92% byweight titania and 8% by weight 5TiO₂.2P₂ O₅. In both cases, the surfacearea retained after firing is shown to be greater for thephosphate-containing material than for the control.

The monolithic supports of this invention may have some catalyticactivity of their own by virtue of the chemistry and structure of thehigh surface area phosphate-containing porous oxide phases.Nevertheless, the support structures of this invention are also intendedto carry additional catalytically active ingredients on the surfacesthereof. (As used herein, the term "surfaces" refers to those surfacesof the monolithic support, including surfaces forming the pore cavities,that are normally intended to be in contact with the work stream ofmaterial to be catalyzed.) This catalytically active material can be anyof the metallic catalysts heretofore used for NOx reduction, for generalchemical processing, or for automotive exhaust catalysis. Preferredcatalytic materials are the transition metals (including the rare earthmetals) and metals of Group IIB. The metals can be used in elementalform or in the form of their oxides. Preferred metals are zinc and suchtransition metals as tungsten, platinum, palladium, molybdenum, iron,manganese, vanadium, and copper. These additional catalytic ingredientscan be deposited on the surfaces of the monolith by methods well knownin the art, such as by preparing a solution or slurry of the materialsfor spraying, dip-coating, or impregnating the monolithic support.

In a particularly preferred embodiment, however, the additionalcatalytic ingredient is admixed directly into the original batch andthen co-extruded and sintered with the porous metal oxide material andphosphate material. Generally the catalytic material is incorporatedinto the batch in an amount of about 3-20 weight percent, preferably5-10 weight percent, based on the total batch weight. In thisembodiment, it is preferred that the admixed catalytic material be inparticulate form with a primary particle size no greater than about 20microns, preferably no greater than about 2.0 microns, and mostpreferably no greater than about 1.5 microns. In one embodiment of theinvention, this reduced particle size is obtained by slurrying the oxideof the catalytic metal, or a precursor therefor, with distilled water,and then adjusting the pH and heating to dissolve the material. Afterall the material is dissolved, a portion of the ceramic oxide materialto be used in the monolithic catalyst support is added to the solution.The resultant mixture is then neutralized, with a slight excess of therequired acid or base, to precipitate very fine particles of thecatalytic metal oxide so that they are substantially intimately admixedwith particles of the porous ceramic oxide. The solids are separated bycentrifugation and the resultant wet cake is then admixed withadditional porous metal oxide material and phosphate material to preparethe monolith as earlier described. As a further alternative, the wetcake remaining after centrifugation can be calcined at a temperature ofabout 250°-300° C. The calcined material is then milled to a size finerthan 100 mesh, preferably finer than 200 mesh. In this form, thematerial contains very fine particles (generally less than about 2.0micron) of catalytic material intimately admixed with finely dividedparticles of the porous metal oxide material. The monolith is thenprepared by admixing this calcined and milled material, as earlierdescribed, with additional porous metal oxide material and phosphatematerial.

In another aspect of this invention, a composite monolith is provided inwhich a high surface area support phase, consisting essentially of thecore metal oxides and 0.5-35% by weight of the phosphate material, iscombined with a separate phase of ceramic material that, upon sintering,provides the actual structural integrity and strength to the monolith.In this embodiment, a pre-formed mixture of the core porous oxidematerial and phosphate material is coextruded with the sinterableceramic structural material in a single step, so that the two phases arephysically integrated in their green states, but the high surface areaphase remains as a separate and discrete phase within the ceramic matrixafter the monolith is fired. Composite monoliths of this kind, in whichthe high surface area support phase is a specific mixture of alumina andsilica, are disclosed in U.S. Pat. No. 4,631,269 issued Dec. 23, 1986,to Lachman et al. The disclosures of this patent, which are herebyincorporated by reference, can be followed to prepare compositemonoliths in which the high surface area support phase is the mixture ofcore porous metal oxide and phosphate material of the present invention.

The following examples are illustrative, but not limiting, of theinvention.

EXAMPLE 1

Three batches of phosphate-containing alumina material (designated belowas 1A, 1B, and 1C) and one control batch (100% alumina, no phosphateaddition) were prepared, extruded, shaped into honeycomb monoliths, andsintered, and their properties tested. The phosphate-containingmonoliths were prepared from batch ingredients as follows:

    ______________________________________                                                           Composition                                                                   (parts by weight)                                          Ingredient           Ex. 1A  Ex. 1B  Ex. 1C                                   ______________________________________                                        Al.sub.2 O.sub.3.H.sub.2 O (CATAPAL-B,                                                             87.4    92.06   76.94                                    Vista Chem. Co.)                                                              Al.sub.2 (OH).sub.5 Cl (CHLORHYDROL 50%,                                                           --      --      8.16                                     aqueous solution,                                                             Reheis Chem. Co.)                                                             Al(H.sub.2 PO.sub.4).sub.3 solution                                                                12.6    --      14.9                                     (50% in water)                                                                (NH.sub.4)2HPO4 (Baker Chem. Co.)                                                                          7.94    --                                       METHOCEL (Dow Chem. Co.)                                                                           6.0     6.0     6.0                                      Distilled water      38.3    40.8    35.0                                     ______________________________________                                    

In each case, the ingredients were combined in a mix muller and thebatch mixed until substantial homogeneity and plasticity were attained.The batch was extruded through a "spaghetti" die two times and thenthrough a shaping die to form honeycomb monoliths of 1-inch (2.54 cm)diameter having 200 square cells per square inch (about 30 cells persquare centimeter). The "control" material was prepared by forming aslurry of 83.5 parts by weight distilled water, 15 parts aluminamonohydrate (DISPURAL, Remet Chem Corp.) and 1.5 parts acetic acid. 40parts by weight of this slurry were then combined, in a mix muller, witha previously-made mixture of 100 parts by weight CATAPAL-B aluminamonohydrate, 6 parts METHOCEL, and 16 parts distilled water. The batchwas mixed and extruded to form a honeycomb as described above. In allcases, the honeycombs were fired at temperatures from 500°-1200° C. forsix hours and their surface area (m² /g) measured by BET. For strengthdetermination, rods of the batch material (approximately 1.3 cm indiameter) were also extruded and fired according to the same schedule,and the modulus of rupture (MOR) of the material was determined asdescribed in U.S. Pat. No. 4,631,267. The results are shown in Table 1below.

                                      TABLE 1                                     __________________________________________________________________________    Firing                                                                             EX. 1A   EX. 1B   EX. 1C   Control                                       Schedule                                                                           SA  MOR  SA  MOR  SA  MOR  SA                                            (6 hours)                                                                          (m.sup.2 /g)                                                                      (psi)                                                                              (m.sup.2 /g)                                                                      (psi)                                                                              (m.sup.2 /g)                                                                      (psi)                                                                              (m.sup.2 /g)                                  __________________________________________________________________________     500° C.                                                                    221.9                                                                             666  226.7                                                                             1930 217.1                                                                              992 190.0                                          750° C.                                                                    200.9                                                                             560  203.6                                                                             2060 197.5                                                                             1143 139.4                                         1000° C.                                                                    125.2                                                                             903  128.3                                                                             1540 133.1                                                                              649  84.4                                         1100° C.                                                                     99.6                                                                             764  100.0                                                                             1860  94.7                                                                              716  6.1                                          1200° C.                                                                     18.3                                                                             1840  15.6                                                                             5440  14.8                                                                             2203 --                                            __________________________________________________________________________

EXAMPLE 2

Batches of alumina material with varying amounts of phosphate materialaddition (designated below as Examples 2A-2F) and a control (100%alumina) were prepared by admixing the materials shown in Table 2 belowand extruding the batched materials to form honeycombs. In examples2A-2F, the indicated alumina and phosphate materials were combined in amix muller with 6.0 parts by weight of METHOCEL and a sufficient amountof distilled water to provide plasticization. The "control" material wasprepared and extruded as described in Example 1. The extruded honeycombswere then fired for 6 hours at 1000° C. and 1200° C. For each example,Table 2 provides the alumina and phosphate batch ingredients as well asthe composition and BET surface area of the fired material.

                  TABLE 2                                                         ______________________________________                                        Batch Composition      Fired Composition                                      (parts by weight)      (weight %)                                             Example (NH.sub.4).sub.2 HPO.sub.4                                                                Al.sub.2 O.sub.3.H.sub.2 O                                                               Al     AlPO.sub.4                              ______________________________________                                        2A      2           98         97.5   2.5                                     2B      5           95         93.8   6.2                                     2C      8           92         89.9   10.1                                    2D      16          84         79.3   20.7                                    2E      24          76         68.3   31.7                                    2F      40          60         44.5   55.5                                    Control 0           100        100    0                                       ______________________________________                                                   Surface Area                                                                             Surface Area                                                       (1000° C.)                                                                        (1200° C.)                                       Example    (m.sup.2 /g)                                                                             (m.sup.2 /g                                             ______________________________________                                        2A         116.1      22.4                                                    2B         127.0      29.2                                                    2C         136.0      29.2                                                    2D         129.4      16.3                                                    2E         77.1       7.9                                                     2F         0.6        0.3                                                     Control    86.8       6.1                                                     ______________________________________                                    

EXAMPLE 3

Batches of titania material with varying amounts of phosphate materialaddition (designated below as Examples 3A-I) and a control (100%titania) were prepared by admixing the materials shown in Table 3 below,according to the procedure described in Example 1. In Examples 3A-I, theindicated titania and phosphate materials were combined in a mix mullerwith 6.0 parts by weight of METHOCEL and a sufficient amount ofdistilled water to provide plasticization. The "control" material wasprepared in similar fashion with the exception that no phosphatematerial was added to the batch. In all cases, the batched material wasdried at 110° C. and then fired for 6 hours at 800° C. For each example,Table 3 provides the titania and phosphate batch ingredients as well asthe composition and BET surface area of the fired material.

                  TABLE 3                                                         ______________________________________                                        Batch Composition Fired Composition                                                                           Surface                                       (parts by weight) (weight %)    Area                                          Example                                                                              (NH.sub.4).sub.2 HPO.sub.4                                                               TiO.sub.2                                                                             P.sub.2 O.sub.5                                                                      TiO.sub.2                                                                            (m.sup.2 /g)                          ______________________________________                                        3A     60         40      44.6   55.4   3.3                                   3B     40         60      26.4   73.6   12.4                                  3C     30         70      18.7   81.3   20.5                                  3D     20         80      11.8   88.2   25.9                                  3E     10         90      5.6    94.4   34.8                                  3F     8          92      4.5    95.5   35.3                                  3G     6          94      3.3    96.7   36.6                                  3H     4          96      2.1    97.9   36.3                                  3I     2          98      1.1    98.9   30.8                                  Control                                                                              0          100     100    0      3.0                                   ______________________________________                                    

EXAMPLE 4

A suspension of 36 grams of zinc oxide in 1200 ml of distilled water wasprepared. To this suspension was added 108 ml of concentratedhydrochloric acid. The resultant mixture was heated, with stirring,until all of the zinc oxide had dissolved. To this solution was thenadded 490.2 grams of titanium dioxide (Degussa Corp. P25) and themixture was then neutralized with 108 ml of concentrated ammoniumhydroxide, which caused a precipitation of the zinc oxide. Theprecipitated solution was centrifuged three times at 7000 rpm for 15minutes, and the recovered solids material was transferred to anevaporating dish and heated at 110° C. until dry. The dried material wascalcined for 3 hours at 300° C. and the calcined material then ballmilled to a particle size finer than 100 mesh. The calcined and milledmaterial was dry-mixed with 36 grams of METHOCEL binder and placed in amix muller, into which was further charged a previously preparedsolution of 37 grams of ammonium biphosphate dissolved in 75 ml ofdistilled water. Tetraisopropyl titanate, 199.8 grams, was then added tothe muller, and the resulting batch was mixed in the presence ofsufficient additional distilled water to plasticize the mixture. Theplasticized material was extruded through a "spaghetti" die and thenthrough a final die to form a honeycomb shape having 300 square cellsper square centimeter of frontal surface area. The extruded honeycombswere dried at 60° C. for 48-72 hours and then at 110° C. for 24 hours,after which they were fired at 500° C. for 6 hours.

EXAMPLE 5

A suspension of 30 grams of ferric oxide (Fe₂ O₃) in 1200 ml ofdistilled water was prepared. To this suspension was added 600 ml ofconcentrated hydrochloric acid. The resultant mixture was heated, withstirring, until all of the ferric oxide had dissolved. To this solutionwas then added 514.8 grams of titanium dioxide (Degussa Corp. P25) andthe mixture was then neutralized with 600 ml of 50% sodium hydroxide(aqueous), which caused a precipitation of the ferric oxide. Theprecipitated solution was centrifuged at 7000 rpm for 15 minutes.Centrifuging was repeated three times and the recovered solids materialwas transferred to an evaporating dish and heated at 110° C. until dry.The dried material was calcined for 3 hours at 300° C. and the calcinedmaterial then ball milled to a particle size finer than 100 mesh. Thecalcined and milled material was dry-mixed with 36 grams of METHOCELbinder and placed into a mix muller, into which was further charged apreviously prepared solution of 37 grams ammonium biphosphate in 75 mlof distilled water. Tetraisopropyl titanate, 200 grams, was added to themuller and the resulting batch was mixed in the presence of sufficientadditional distilled water to plasticize the mixture. The plasticizedmaterial was extruded through a "spaghetti" die and then through a finaldie to form a honeycomb shape having about 30 square cells per squarecentimeter of frontal surface area. The extruded honeycombs were driedat 60° C. for 48-72 hours and then at 110° C. for 24 hours, after whichthey were fired at 500° C. for 6 hours.

EXAMPLE 6

A suspension of 36 grams of manganese dioxide in 1200 ml of distilledwater was prepared. To this suspension was added 828 ml of concentratedhydrochloric acid. The resultant mixture was heated with stirring untilall of the manganese dioxide had dissolved. To this solution was thenadded 490.2 grams of titanium dioxide (Degussa Corp. P25) and themixture then neutralized with 792 ml of concentrated ammonium hydroxide,which caused a precipitation of the manganese dioxide. The precipitatedsolution was centrifuged at 7000 rpm for 15 minutes. Centrifuging wasrepeated three times and the recovered solids material was transferredto an evaporating dish and heated at 110° C. until dry. The driedmaterial was calcined for 3 hours at 300° C. and the calcined materialthen ball milled to a particle size finer than 100 mesh. The calcinedand milled material was dry-mixed with 36 grams of METHOCEL binder andplaced into a mix muller, into which was further charged a previouslyprepared solution of 37 grams ammonium biphosphate in 75 ml of distilledwater. Tetraisopropyl titanate, 200 grams, was added to the muller andthe resulting batch was mixed in the presence of sufficient additionaldistilled water to plasticize the mixture. The plasticized material wasextruded through a "spaghetti" die and then through a final die to forma honeycomb shape having 200 square cells per square inch of frontalsurface area. The extruded honeycombs were dried at 60° C. for 48-72hours and then at 110° C. for 24 hours, after which they were fired at500° C. for 6 hours.

What is claimed is:
 1. A fired monolithic structure consisting ofA)80-100% by weight of a sintered ceramic phase of(a) a porous metal oxidematerial consisting of (i) 50-100% by weight of titania, zirconia,titania-zirconia mixtures, titania-alumina mixtures, zirconia-aluminamixtures, or zirconia-alumina-titania mixtures; and (ii) 0-50% by weightof a ceramic metal oxide material other than alumina, titania, orzirconia; and (b) P₂ O₅ substantially dispersed throughout the porousmetal oxide material in an amount of about 0.5 -15% by weight, based onthe total weight of the P₂ O₅ and component (i); and B) 0-20% by weightof catalytic material selected from the group consisting of catalyticmetal and catalytic metal oxide.
 2. The monolithic structure of claim 1in which said porous metal oxide material consists of 80-100% by weightof the oxides of component (i) and 0-20% by weight of the oxides ofcomponent (ii).
 3. The monolithic structure of claim 1 in whichsubstantially all the porous metal oxide material is titania and inwhich said sintered ceramic phase consists of about 1.5-15 weightpercent P₂ O₅, based on the total weight of titania and P₂ O₅.
 4. Themonolithic structure of claim 1 in which substantially all the porousmetal oxide material is titania, substantially all the P₂ O₅ is in theform of 5TiO₂.2P₂ O₅, and said P₂ O₅ compound constitutes about 5-12weight percent of the structure.
 5. The monolithic structure of claim 1in which substantially all the porous metal oxide material is zirconiaand in which said sintered ceramic phase consists of about 1-15 weightpercent P₂ O₅, based on the total weight of zirconia and P₂ O₅.
 6. Themonolithic structure of claim 2 which is in the form of a catalystsupport and which consists of 3-20% by weight of said catalyticmaterial, said catalytic material being selected from the groupconsisting of transition metals, Group IIB metals, and oxides of these.7. The monolithic catalyst support of claim 6 wherein the catalyticmaterial is selected from the group consisting of zinc, molybdenum,vanadium, manganese, tungsten, copper, iron, platinum, palladium, andoxides of these.
 8. The monolithic catalyst support of claim 6 whereinthe catalytic material is selected from the group consisting ofplatinum, palladium, platinum oxide, palladium oxide, and mixtures ofthese.
 9. The monolithic structure of claim 2 which is a fluid filter inthe form of a honeycomb having about 4-370 cells per square centimeterof surface area.
 10. The monolithic structure of claim 1 in which saidceramic metal oxide material of component (ii) is present in an amountup to 50% by weight of said porous metal oxide material and is selectedfrom the group consisting of cordierite, mullite, clay, talc, spinels,silicates, aluminates, aluminum titanates, aluminum titanate solidsolutions, silica, glasses, glass ceramics, and mixtures of these.
 11. Amethod of producing a fired monolithic structure comprising the stepsof:A) admixing, into a substantially homogeneous batch, componentsconsisting of(1) 80-100% by weight of ceramic phase material consistingof(a) a porous metal oxide material consisting of (i) 50-100% by weightof titania, zirconia, titania-alumina mixtures, zirconia-aluminamixtures, or zirconia-alumina-titania mixtures; and (ii) 0-50% by weightof a sinterable ceramic metal oxide material other than alumina,titania, or zirconia; and (b) P₂ O₅ or a precursor therefor in an amountsufficient to provide, after firing, about 0.5-15% by weight of P₂ O₅based on the total weight of the P₂ O₅ and component (a)(i); and (2)0-20% by weight of at least one catalytic material selected from thegroup consisting of catalytic metal and catalytic metal oxide; B)forming said batch into a desired shape; and C) firing the shape. 12.The method of claim 11 in which said porous metal oxide materialconsists of 80-100% by weight of the oxides of component (i) and 0-20%by weight of the oxides of component (ii).
 13. The method of claim 11 inwhich the P₂ O₅ is admixed into said batch in the form of phosphoricacid, dibasic ammonium phosphate, or alumina dihydrogen phosphate. 14.The method of claim 11 in which substantially all the porous metal oxidematerial is titania and in which sufficient P₂ O₅ material is providedto generate about 1.5-15 weight percent P₂ O₅ in the monolith followingfiring.
 15. The method of claim 11 in which substantially all the porousmetal oxide material is zirconia and in which sufficient P₂ O₅ isprovided to generate about 1-15 weight percent P₂ O₅ in the monolithfollowing firing.
 16. The method of claim 12 in which said batchconsists of 3-20% by weight of said catalytic material, said catalyticmaterial being selected from the group consisting of transition metals,Group IIB metals, and oxides thereof, and said catalytic material beingin particulate form with an average primary particle size of up to about20 microns.
 17. The method of claim 16 in which said catalytic materialhas an average primary particle size of up to about 2.0 microns and isselected from the group consisting of zinc, vanadium, molybdenum,tungsten, palladium, platinum, iron, manganese, copper, and oxides ofthese.
 18. The method of claim 16 in which said catalytic materialconsists of platinum, palladium, platinum oxide, palladium oxide, or amixture of these.
 19. The method of claim 11 in which said ceramic metaloxide material of component (ii) is present in an amount up to 50% byweight of said porous metal oxide material and is selected from thegroup consisting of cordierite, mullite, clay, talc, spinels, silicates,aluminates, aluminum titanate, solid solutions of aluminum titanate,silica, glasses, glass ceramics, and mixtures of these.
 20. A compositemonolithic catalyst support structure consisting ofA) 80-100% by weightof a ceramic support material that is(a) a sintered material consistingof (i) 50-100% by weight of titania, zirconia, titania-zirconiamixtures, titania-alumina mixtures, zirconia-alumina mixtures, orzirconia-alumina-titania mixtures; and (ii) 0-50% by weight of a ceramicmetal oxide material other than alumina, titania, or zirconia, whereincomponents (i) and (ii) exist as separate phases; and (b) P₂ O₅substantially dispersed throughout the phase of component (i) in anamount of about 0.5-15% by weight, based on the total weight of the P₂O₅ and component (i); and B) 0-20% by weight of at least one catalyticmaterial selected from the group consisting of catalytic metal andcatalytic metal oxide.
 21. The composite structure of claim 20 in whichsubstantially all of component (i) is titania and in which said P₂ O₅ ispresent in an amount of about 1.5-15% by weight, based on the totalweight of the P₂ O₅ and titania.
 22. The composite structure of claim 20in which substantially all of component (i) is zirconia and in whichsaid P₂ O₅ is present in an amount of about 1-15% by weight, based onthe weight of the P₂ O₅ and zirconia.
 23. The composite structure ofclaim 20 in which component (ii) is present in an amount up to 50% byweight of said sintered material (a) and is selected from the groupconsisting of cordierite, mullite, clay, talc, spinels, silicates,aluminates, aluminum titanate, solid solutions of aluminum titanate,silica, glasses, glass ceramics, and mixtures of these.